This invention relates to a sleeve-type fluid flow diverter, particularly for use in the cleaning of tubing of heat exchangers.
It has previously been suggested that heat exchanger tubing may be internally cleaned by mounting brush-basket assemblies on the ends of the tubes, and then by flowing fluid first in one direction and then the other to cause the brushes to traverse the length of the tubes and then return to their original position. See the above-identified U.S. Pat. No. 3,319,710.
It has also previously been suggested as in the above-identified U.S. Pat. No. 3,973,592 to utilize a four-way valve for purposes of reversing fluid flow within the tubes to cause the cleaning brushes to move in both directions within the tubes.
It is also broadly known to utilize a sleeve-type diverter to reverse the fluid flow within the tubes. This known device incorporated a generally cylindrical sleeve rotatably mounted in an outer housing. The housing provided annular ring type support bearing surfaces for the ends and center portion of the sleeve and also included four ports for connection through conduits to a source of cooling fluid and to the heat exchanger. On one side of the sleeve axis, a first pair of housing ports for supply and return, were provided for connection to the source of cooling fluid. On the opposite side of the axis, and in line with the supply and return ports, a second pair of housing ports was provided, each of which could be selectively connected to either the inlet or outlet of the heat exchanger, depending on the rotary position of the sleeve.
The sleeve body of the prior diverter included a large plurality of ports adapted to selectively register with the housing ports. Connector conduits disposed within the sleeve and of a diameter at least as great as the housing and sleeve ports served to form a plurality of internal sleeve chambers and to connect the first and second housing ports. In each of the two rotary positions of the sleeve, fluid flowed from the housing supply port and either through or around one of the sleeve's internal conduits to one of the second pair of housing ports. At the same time, fluid flowed from the other of the second pair of housing ports and either through or around the other of the sleeve's internal conduits to the housing return port. Rotation of the sleeve 90.degree. reversed the flow at the second pair of housing ports, although the flow at the supply and return housing ports remained the same.
In the above described known sleeve-type diverter, it was found that the large restriction within the sleeve, caused by the connector conduits, caused an undesirable pressure drop in the fluid flowing around a particular conduit. In addition, it was found that binding sometimes occurred between the annular support bearing surfaces and the sleeve wall, thus making it difficult to install or rotate the sleeve. Aside from considerations of manufacturing tolerances, this binding was believed to be at least partially due to corrosion and sticking of particles occurring at the continuously mating interfaces between the bearing surfaces and sleeve.
The present invention solves the aforementioned problems and is directed to a sleeve-type diverter which substantially reduces pressure drop as well as binding difficulties. It is also more economical to manufacture.
In accordance with one aspect of the invention, the rotatable sleeve is mounted for rotation on an axle means and is spaced inwardly from the housing walls. The sleeve forms a single internal chamber through which fluid always flows in the same direction in both operative positions of the sleeve. The space between the sleeve and housing also forms a single chamber through which fluid always flows in the same direction in both operative positions of the sleeve. The unidirectional fluid flow through the sleeve itself is opposite to the unidirectional fluid flow through the external chamber between the housing and sleeve. The only restriction to fluid flow within the sleeve is the sleeve axle means, which has a substantially smaller cross-sectional area than that of the sleeve and housing ports, thus reducing pressure drop to a minimum. Likewise, the length of the cross-sectional area between the inner sleeve and housing is much larger than the cross-sectional area of a connected port, thus contributing very little to pressure drop.
In accordance with another aspect of the invention, the supporting connection between the cylindrical sleeve and housing walls occurs adjacent the registered sleeve and housing ports by means of mating peripheral surfaces. The machining of the surfaces can be such as to provide for a substantially close fit. In addition, in either position of the sleeve, the unused or unregistered sleeve ports face the interior wall of the housing with their supporting surfaces spaced therefrom. A filler member is mounted to the housing interior wall adjacent the position of each unregistered sleeve supporting surface and is formed to also provide a close fit therewith. The total area of contact between the various surfaces is less than the contacting bearing surfaces of the prior known sleeve-type diverter, thus reducing binding due to tolerance problems.
In actual use of a diverter in connection with a tube type heat exchanger or similar process device, there will be a fluid pressure differential between the supply and return sides within the diverter itself, due to the pressure drop caused by the tube restrictions. The supply side will have a higher pressure than the return side. The result is that water from the supply side will tend to flow through the narrow gaps between the sleeve supporting surfaces and the housing supporting surfaces and/or the filler members in a direction from the supply or high pressure side toward the return or low pressure side. The direction of flow through the gaps will be the same for both rotary positions of the sleeve, due to the aforementioned unidirectional fluid flow. Any loose particles of corrosion products which may appear at the various gap interfaces will tend to be washed through to the other side and not get stuck. Freely exposed contact surfaces will also be continuously washed, whether the sleeve is in or between its operating positions. This also will reduce problems of binding .